Nonwoven webs formed by a variety of processes including meltblown and spunbonded processes which may be coated with polymeric compositions are well known for a wide variety of end uses, such as wipes, surgical gowns, dressings, bags and the like. An example of such an end use is disclosed in U.S. Pat. No. 4,535,481 which describes a surgical gown made from a spunbonded/meltblown/spunbonded fabric having a basis weight of 1.4 oz/yd.sup.2 provided with a 1.25 mil thick film of low density polyethylene with 9% ethylene vinyl acetate extrusion-laminated to the fabric.
U.S. Pat. No. 4,211,692 discloses extrusion coating compositions which employ an ethylene-propylene-diene terpolymer rubber, a high density polyethylene, an ethylene-propylene block copolymer or an ethylene-isobutylacrylate copolymer for woven and nonwoven polyolefin substrates.
U.S. Pat. No. 4,684,568 discloses a process for preparing fabrics that are permeable to moisture vapor and impermeable to liquid water consisting essentially of the steps of applying a continuous coating of polypropylene to a surface of a vapor and liquid permeable, fibrous sheet and then calendering the coated surface. The fabrics are disclosed as being suited for use as roofing-tile underlayment and air-infiltration barriers for buildings.
Composites of self-bonded, fibrous, nonwoven web and woven fabric composites are generally disclosed in U.S. patent application Ser. No. 556,353, filed on Jul. 20, 1990, in the name of Geraldine M. Eaton, et al., and U.S. patent application Ser. No. 556,354, filed on Jul. 20, 1990in the name of Paul N. Antonacci, et al., both commonly assigned to the present assignee. No specific details of construction or end use are described for these composites in these applications.
Spunbonded processes can produce polymeric nonwoven webs by extruding a multiplicity of continuous thermoplastic polymer strands through a die in a downward direction onto a moving surface where the extruded strands are collected in a randomly distributed fashion. The randomly distributed strands are subsequently bonded together by thermobonding or by needlepunching to provide sufficient integrity in a resulting nonwoven web of continuous fibers. One method of producing spunbonded nonwoven webs is disclosed in U.S. Pat. No. 4,340,563. Spunbonded webs are characterized by a relatively high strength/weight ratio, isotropic strength, high porosity and abrasion resistance properties but generally are nonuniform in properties such as basis weight and coverage.
A major limitation that multilayer composites and laminates containing spunbonded nonwoven webs laminated to other nonwoven and woven fabrics is that the spunbonded nonwoven web used to impart strength to the multilayer composites and laminates, especially strength in the cross-machine direction, is nonuniform in coverage and basis weight. In many applications, attempts are made to compensate for poor fabric aesthetics and limited physical properties that result from this nonuniformity in coverage and basis weight by the use of spunbonded webs that have a greater number of filaments and heavier basis weights than would normally be required by the particular application if the spunbonded web had a more uniform coverage and basis weight. This, of course, adds to the cost of the composite and laminate products and contributes undesirable features such as stiffness to these products.
In view of the limitations of spunbonded nonwoven webs, there remains a need for improved multilayer composites and laminates, particularly, those wherein a self-bonded, fibrous nonwoven web having very a uniform basis weight and coverage as measured by a Basis Weight Uniformity Index determined from average basis weights having standard deviations of less than 10% is used for at least one layer and which is adhered to at least one layer of suitable thermoplastic yarns in the form of woven fabric such as wall covering fabric, softside luggage fabric, leno weave fabric and the like.
It is an object of this invention to provide improved composites of nonwoven webs and woven fabrics. It is a further object of this invention to provide improved self-bonded, fibrous, nonwoven web and woven fabric composites comprising at least one layer of a uniform basis weight, self-bonded, fibrous, nonwoven web adhered to at least one layer comprising woven thermoplastic yarns by a polymeric composition. Other objects of this invention will be apparent to persons skilled in the art from the following description and claims.
We have found that the objects of this invention can be attained by providing self-bonded, fibrous nonwoven web and woven fabric composites comprising at least one layer of a uniform basis weight, self-bonded, fibrous, nonwoven web comprising a plurality of substantially randomly disposed, substantially continuous thermoplastic filaments wherein the web has a Basis Weight Uniformity Index of 1.0.+-.0.05 as determined from average basis weights having standard deviations of less than 10% adhered to at least one layer comprising woven thermoplastic yarns. In a preferred embodiment of the invention, these objects are achieved by using a thermoplastic composition to adhere the self-bonded nonwoven web and woven layers.
The objects of this invention can be further attained by providing composites comprising at least one layer of the uniform basis weight, self-bonded, fibrous, nonwoven web laminated to at least one layer of a woven wall covering fabric, a woven softside luggage fabric or a leno fabric by means of a polymeric composition in the form of a hot melt adhesive, an extrusion coating composition or a water-based adhesive or by a calendering process.
Among the advantages produced by the softside luggage fabric of this invention are less yarn ravel, thereby improving sewn seam strength, and a degree of waterproofness provided to the composite structure by replacing the typical waterproof coatings applied to the backside of the fabric with a layer of the uniform basis weight self-bonded, nonwoven web and a polymeric composition in the form of a hot melt adhesive, an extrusion coating composition or a water-based adhesive.
Advantages produced by the wall covering fabric of this invention include a more uniform and reproducible surface on the backside of the wall covering fabric which aids in significantly decreasing or eliminating strike-through of backcoating through the wall covering fabric, especially those wall covering fabrics having an open weave. The self-bonded web also provides a semiporous layer to which wall covering adhesive can adhere and bond the wall covering composite to a wall surface without wall covering adhesive coming through the wall covering to the face of the fabric.
Advantages of the leno fabric comprising a layer of a self-bonded, nonwoven web adhered to a layer of woven thermoplastic yarns in the form of a leno weave include a fabric useful for the recovery of oil from oil spills on bodies of water. The self-bonded, nonwoven web made of polypropylene can take up oil as well as hold in place other oil take-up materials behind the open leno weave which provides support. With the materials formed from polypropylene, the oil recovery fabric will float on the water.